Why did the Lochner v. New York majority reject the claim that shorter bakery hours protected public health?

In Lochner v. New York, the Supreme Court majority rejected the claim that limiting bakery hours protected public health because it concluded that baking was not a dangerous or unhealthful trade that required special state regulation.1

Writing for the majority, Justice Rufus Peckham argued that the law was an unconstitutional infringement on the freedom of contract, a liberty protected by the due process clause of the Fourteenth Amendment. To justify the state's interference with this freedom, the law would have needed to be a valid exercise of police power aimed at protecting public health or the health of workers.1

The Court found no evidence that baking posed such risks, relying on data suggesting that the mortality rate of bakers was not higher than that of other professions. Consequently, the majority asserted that the quality of bread did not depend on whether a baker worked ten hours a day or sixty hours a week, and therefore, the hours provision failed to qualify as a legitimate health measure.1